Marsden et al. Industrial & Engineering Chemistry Product Research and Development, 19 551 (1980) were the first to show that an active low temperature methanol synthesis catalyst can be produced by leaching small particles of a Cu-Al-Zn alloy in sodium hydroxide solutions. In other studies, Friedrich et al. J. Catal. 80 1, 14 (1983) and Bridgewater et al. Appl. Catal. 7 369 (1983) using small particles, have investigated the effect of alloy composition on catalyst activity. This technique of catalyst preparation has been fully described in U.S. Pat. No. 4,349,464 and U.S. Pat. No. 4,366,260.
A recent study, Curry-Hyde et al. Appl. Catal. 29 31 (1987) has been concerned with the preparation of catalysts by the method described in the patents. In this study, an alloy of optimal composition was used to study preparation and characteristics of the Raney catalyst in pellet form. It was found that the long times required to leach the large particles had two detrimental effects on the nature of the catalyst. The first decreased the overall pellet surface area after long periods of leaching, whilst the second caused a decrease in the specific activity of the catalyst.
The decrease in pellet surface area was as a result of the physical rearrangement of copper crystallites in the porous copper whilst the alloy core was still being leached. The decreased activity resulted from decreases in zinc oxide concentrations on the copper surface. These were caused by secondary leaching effects on the zinc oxide that become significant at long leach times.
Previous investigations sought to improve the zinc oxide content in the leached Cu structures by changing the ZN content of the Al-Cu-Zn alloy, as described in Friedrich et al. J. Catal. 80 1, 14 (1983) and Bridgewater et al. Appl. Catal. 7 369 (1983).